1. Field of the Invention
The present invention relates to a surgical treatment apparatus to treat a living tissue.
2. Description of the Related Art
A specification in European Patent No. 893971 discloses an ultrasonic treatment apparatus as a surgical treatment apparatus. In the ultrasonic treatment apparatus, a surgical instrument is attachable to/detachable from a handpiece assembly. A horn to expand and transmit ultrasonic vibration is inserted through the handpiece assembly. A transmission rod to transmit the ultrasonic vibration is inserted through a cylindrical housing of the surgical instrument. A distal end portion of the housing has a narrow inside diameter and a step surface formed thereon, a flange is formed on the transmission rod, and an elastic member is interposed between the step surface and the flange. The distal end portion of the handpiece assembly and a proximal end portion of the surgical instrument are coupled with each other, and so a distal end portion of the horn in the handpiece assembly and a proximal end portion of the transmission rod in the surgical instrument are pressed against and coupled with each other. As a method of coupling the handpiece with the surgical instrument, screwing is adopted and besides, there are snap-on coupling and twisting lock fitting.